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June 30, 2017 -- Egypt has unveiled the first national diagnostic reference levels (DRLs) for CT, but senior radiologists still have concerns about radiation dose. Areas for improvement include the selection of exposure parameters for different examinations, taking into account the image quality, with particular attention on facilities using consistently higher doses compared with DRLs.

Initiated under the regional technical cooperation project of the International Atomic Energy Agency (IAEA), the researchers collected data from more than 3,700 individual patients undergoing CT scans and then compared them with the DRLs of various foreign countries. They found a consistent problem with scan range, because DRLs for dose-length product (DLP) were not corresponding with DRLs for CT dose index volume (CTDIvol).

"This first-ever survey of CT practice in Egypt demonstrated the need to improve training of health professionals involved in CT on factors influencing image quality, dose, and protocols optimization," wrote the research team, led by Dr. Dina Husseiny Salama, professor and head of radiology at the National Center for Radiation Research and Technology in Cairo and the Egyptian Atomic Energy Authority (Physica Medica, July 2017, Vol. 39, pp. 16-24).

Promoting good practice

Inherent in properly administering CT is knowing whether doses are too high or too low, which is where DRLs come in -- they act as a reference to compare practices so individual facilities may determine if they're fitting in. DRLs are based on wide-scale surveys of a locality. Even though DRLs have international support, most surveys come from Europe.

"In Europe, there is a culture of nationally driven actions because of Euratom and its associated mandatory actions by European member states," noted Madan Rehani, PhD, who was a part of the research team and was a radiation safety specialist in the Radiation Protection of Patients Unit of the IAEA. Currently, he is the director of Global Outreach for Radiation Protection Program at Massachusetts General Hospital in Boston, U.S.

The 2016 IAEA technical meeting on DRLs in Vienna. Dr. Dina Husseiny Salama is third from the left in the front row, and Madan Rehani, PhD, another study author, is fifth from the left. Image courtesy of Dr. Dina Husseiny Salama.

"Outside of Europe, actions are normally driven by enthusiasts that create momentum and slowly may spread to others in the country by the approach of "not being left out" in a desired good action," he told AuntMinnieEurope.com.

The group conducted a large-scale prospective study of 3,762 patients to establish national DRLs for CT in the adult population. Of the approximately 250 CT facilities across Egypt, 50 met the researchers' eligibility criteria. The sites cover all 27 governorates and include facilities from the university, military, governmental, and private sectors.

The researchers identified the six most frequent CT procedures: head, chest (high-resolution), abdomen (for liver metastases), abdomen-pelvis, chest-abdomen-pelvis, and CT angiography (aorta and both lower limbs). They used median DLP and CTDIvol data from each site to estimate the typical dose in each facility and based the national DRLs on the rounded third quartile of these values.

National DRLs and achievable doses

CT protocol

Egyptian DRL

Achievable dose

CTDIvol per sequence, mGy

DLP per examination, mGy-cm

CTDIvol per sequence, mGy

DLP per examination, mGy-cm

Head

30

1,360

28

88.5

Chest (high-resolution)

22

420

17

320

Abdomen (liver metastasis)

31

1,425

28

990

Abdomen-pelvis

31

1,325

27

875

Chest-abdomen-pelvis

33

1,320

30

1,040

CT angiography (aorta and lower limbs)

37

1,320

30

1,105

"Before initiating this study, worse scenarios were expected in terms of very high DRLs in CT examinations in Egypt; however, surprisingly, the results of this study do not raise red flags of consistent high doses as compared with other countries," Husseiny Salama told AuntMinnieEurope.com.

How the results compare

The Egyptian DRL of CTDIvol for the head is half of that of other countries, and for other exams, the DRLs are much higher, which could be explained by the inconsistent use of protocol for the same clinical indication, lesser frequency in use of automatic tube current modulation as compared with other facilities, and the number of sequences is higher in Egypt, according to the researchers. The last factor is important and needs further evaluation, they added.

Other elements requiring analysis are the variations in CT parameters among sites, among sites with similar equipment, and correlation of exposure factors and dose with patient size.

"The study highlights a need to modify practice as there cannot be justification for lesser use of tube current modulation in the body region as compared with the head," the authors wrote.

Changing practice requires more work on optimization and corrective actions, starting with direct feedback to the hospitals, investigation of calibration and protocol settings especially with scan range, promotion of DRL-training activities, and motivating all departments to compare their doses with DRLs, according to Husseiny Salama.

As a consequence of undertaking this study, the Egyptian medical facilities and health ministry professionals are already working together to proactively address radiation protection.

"In this project, the motivation has been high among the team rather than doing it without enthusiasm and having heart in the action simply to comply with requirements," she wrote. "If one had to wait for issuance of regulations requiring the establishment of DRLs and wait for the implementation process, it would have taken ages."

In terms of future research, the team plans to proceed with another publication on the optimization and corrective actions the group identified. Also, DRLs are catching on: Many African countries were motivated by this study and are planning to develop their own national DRLs, according to Husseiny Salama. She is supporting African countries through regional IAEA technical cooperation projects in this effort.